1. Field of the Invention
The present invention relates to a disk drive, particularly a magnetic-disk drive and a crash stop which regulates a range of rotation of the actuator of the magnetic-disk drive. More particularly, the invention relates to a crash stop which is capable of adjusting the setting of shock absorptivity with the same elastic material and where the mounting-demounting operation is easy.
2. Description of Related Art
Generally, a magnetic-disk drive includes a magnetic disk which is a data storage medium and an actuator which moves a magnetic head along the surface of the magnetic disk. The actuator is equipped with a carriage which is rotatably fitted on a rotational shaft and a voice coil motor (VCM) which drives this carriage. The carriage is provided with a head arm, on the front end of which the magnetic head is mounted. Also, the carriage is provided with a stopper arm on the carriage surface opposite to the head arm across the rotational shaft. This stopper arm has the voice coil of the VCM mounted thereon. The VCM has the aforementioned voice coil, lower and upper yokes disposed above and under the stopper arm, and a magnetic circuit formed by permanent magnets. The VCM drives the carriage, thereby rotating the head arm. This causes the magnetic head mounted on the front end of the head arm to move over a predetermined position on the disk surface to record data on the magnetic disk or read out recorded data from the magnetic disk.
A magnetic-disk drive such as that described above is provided with a crash stop for prescribing the range of rotation of the actuator. The crash stop is abutted by the stopper arm, thereby prescribing the aforementioned range of rotation. The crash stop is typically comprised of an inner crash stop that prescribes the innermost circumference to which the magnetic head can move on the magnetic disk surface and an outer crash stop that prescribes the outermost circumference to which the magnetic head can move. The inner and outer crash stops, therefore, are provided on both ends of the range of rotation of the stopper arm.
Examples of crash stops found in the art include those having an elastic body such as rubber, or alternatively those comprised of a metal pin such as a stainless steel pin. The crash stop comprising an elastic body has the disadvantages that it lacks the mounting stability and the range of rotation of the actuator will fluctuate due to a displacement in the portion that the stopper arm abuts. In the crash stop comprising a metal pin, the range of rotation of the actuator does not fluctuate but absorption of shock is insufficient, and thus when the actuator runs recklessly and crashes on the crash stop there is the possibility that it will damage a disk surface.
Additionally, there are found crash stops having both the shock absorptivity of an elastic body and the mounting stability of a metal pin, which are comprised of a structure where a metal pin is covered with an elastic body. The shock absorptivity of this crash stop, however, generally becomes smaller than that of a crash stop comprising an elastic body alone. This crash stop is attached to the bottom portion (referred to as the base) of an enclosure or an upper yoke or a lower yoke, for example, by screws.
It is not easy to adjust or vary the shock absorptivity of the conventional crash stop comprising a metal pin covered with an elastic body. Particularly, in the case where design change is performed from a crash stop comprising an elastic body alone to a crash stop comprising a metal pin and an elastic body, if the elastic material used in the crash stop comprising an elastic body alone is employed as it is, there will arise a need to enhance the shock absorptivity, because the shock absorptivity will be worse than that of the crash stop with an elastic body alone. As a countermeasure for this, it is conceivable to change the elastic body to an even softer, elastic body or to thicken the elastic body. However, the elastic materials that can be used are often limited to materials that have been used so far, to avoid the having to test whether new elastic materials are suitable to the interior of the disk drive. For this reason, in many cases, materials with desired shock absorptivity cannot be used. Also, if the thickness of an elastic body is varied, the mounting position of the crash stop must be changed according to that variation, or the diameter of the metal pin must be varied, and consequently, other components will be obliged to be redesigned.
During the disk drive assembly process, after magnetic disks are incorporated into the enclosure, then the carriage is fitted on the rotational arm, and after the magnetic head is moved over the surface of the magnetic disk by rotation of the carriage, or furthermore, after the upper yoke is incorporated, the crash stop is mounted. This is because the mounting and demounting of the carriage will not be able to be performed, if the crash stop is first mounted.
In addition, because the mounting of the crash stop is performed in the end of the assembling process of the magnetic-disk drive and the crash stop needs to be first demounted when the magnetic head or carriage is repaired, other disposed components will be hindrances and there will arise the problem that the mounting-demounting operation will be troublesome.
It therefore can be seen that there is a need in the prior art to provide a crash stop which is capable of adjusting shock absorptivity with the same elastic material and where the mounting-demounting operation is easy.